Kai Gallivan of Yarmouth and his dad Kerry found just the right Huffy on Sunday at the Great Maine Bike Swap at the University of Southern Maine. They were among hundreds who attended the event sponsored by the Bicycle Coalition of Maine, USM’s Office of Environmental Sustainability and the student-run Public Interest Research Group at Sullivan Gym. (Michael Barriault photo)Hundreds of southern Maine bicycle enthusiasts showed up at University of Southern Maine’s Sullivan Gym on Sunday for the Great Maine Bike Swap. (Michael Barriault photo)